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Understanding David Hume

 David Hume pencil drawing

In the eighteenth century, the words “natural religion” referred to religious beliefs based on reason and evidence instead of revelation. In Understanding David Hume, Professor Laurence Houlgate has written and designed a philosophy study guide that helps serious students get through the labyrinth of arguments for and against the existence and infinite nature of God, focusing mainly on the famous Design argument that was popular in Hume’s day and still persists in contemporary philosophical discussions.

Lengthy dialogues between two or three speakers are broken down into discrete and understandable short chapters, allowing students to easily navigate through the book. However, this is not one of the “information” study guides that are so prevalent in the study guide.  Understanding David Hume is a philosophy study guide for smart students who want to think critically about what the author writes not memorize passages so they can get through  a multiple-choice exam.

Questions for thought and discussion and ideas for student essays and term papers are to be found at the conclusion of each section

Here is a sample of what you will find in the book:

 The Design Argument for the Existence of God

Hume begins by pointing out that the Design Argument is analogical. If it is analogical, then it is inductive. If it is inductive then it gives probability, not certainty to the conclusion (2.2 supra). Arguments that give probability are a part of scientific, not philosophical methodology.

The analogy promoted in the Design Argument is between natural things in the universe like animals and artificial (man-made) things like clocks and pianos. Both have “design,” meaning that natural things in the universe have parts that work together for “an end” in the same way that the parts of a clock work together to display the time of day. For example, the delicate parts of an animal’s eye work together to create sight. The chemical elements that compose the sun work together to create light.  Because the animal and the eye “resemble exactly” artificial machines like clocks and pianos, the proponent of the design argument in Hume’s imagined dialogue refers to the eye and the sun as “natural machines.”  The resemblance is to be found in “the curious adapting of means to ends.”

Here is how David Hume has the character Cleanthes tell the remainder of the design argument to his friends Philo and Demea:

 “Since, therefore, the effects resemble each other, we are led to infer by all the rules of analogy, that the causes also resemble, and that the Author of Nature is somewhat similar to that of the mind of man, though possessed of much larger faculties proportioned to the grandeur of the work which he has executed.” (14).

By “the rules of analogy,” Hume means both the form and the content of analogical arguments.  Here is the form:

1. P is the cause of effects a, b and c.

2. Q is the cause of effects a, b and c.

3. P is the cause of effect d.


4. Q (probably) is the cause of effect d.

In Hume’s words, the argument form is a posteriori (empirical), not a priori (analytic). The type of argument is inductive.  This means that the premises give probability (not certainty) to the conclusion.

The inductive argument form is analogical.  In premises 1 and 2, an analogy or similarity of effects (a, b and c) have similar causes (P and Q). Premise 3 states an additional effect (d) of one of these causes (P). It is concluded (in 4)  that the other object or event (Q) probably is the cause of the same effect (d).

 Degrees of probability

Unlike the certainty of valid deductive arguments, the probability of inductive arguments comes in several degrees, beginning with low probability and ending with high probability.  By using the argument form above (18.1), suppose that on the first day of a college philosophy class, Pandorf notices that the book (P) she is holding (e.g. Plato’s Republic) has the same dust cover as the book (Q) Bengrit is holding.  Both dust covers are (a) of the same color, (b) have the same title and (c) have the same author’s name imprinted on the cover. Pandorf knows that her book is Plato’s Republic (d), not some other book. She infers from this resemblance that it is highly probable that removing the dust covers will reveal that Bengrit has the same book (d).

 If the premises of an analogical argument deliver high probability to the conclusion, then the premises must contain sufficient evidence to support that degree of probability.  If Pandorf sees Bengrit holding a large book with no dust cover, then she must adjust the degree of probability for the conclusion that Bengrit’s large book is the same as her dust-covered book. Having only a large book in his hand is not sufficient evidence to conclude that it is “highly probable” that Bengrit is holding a copy of Plato’s Republic. The word “perhaps” is more suitable.

And the evidence must be relevant.  If Bengrit is holding a hat or an ice cream cone, this has nothing to do with the conclusion.


“A very weak analogy”

In his criticism of the Design Argument, Hume is aware of all this, and more. The character Philo says that Cleanthes has given “a very weak analogy” because the similarity of the natural world to the artificial is “much less than exact.” (16). We know from experience that pianos and clocks are the product of intelligent design and construction.  We have no similar experience of intelligent design and construction of an animal eye, a head of cabbage, or the universe itself.  We have no experience of an intelligent being planning and constructing a human eye, a head of cabbage, or a universe.  All the proponents of the Design Argument have to go on is the weak analogy between the parts and interaction of parts in both natural and artificial things.

The fact that we have never experienced an intelligent designer building a universe, a world, a head of cabbage or an animal eye does not mean that we have not experienced or experimented with the cause of each of these natural things.  For example, scientists have discovered that “three embryonic tissue sources—the neural ectoderm, the surface ectoderm, and the periocular mesenchyme—contribute to the formation of the mammalian eye.” (Heavner and Pevney)  The authors of this article also write that “the developing eye has presented an invaluable system for studying the interactions among cells and, more recently, genes, in specifying cell fate.”

The words “an invaluable system for studying the interactions among cells and genes” trigger an alarm for a response from the Design Argument proponents. They will say that a system with cell and gene interactions can only have been caused by an intelligent designer.

But this response begs the question, “How do you know that such interactions can only be caused by an intelligent designer? Show us the evidence that supports this. If you can’t provide the evidence, then you are assuming the very thing that you want to prove!” 

Philo makes the point that because Cleanthes is a human being, he is biased about “thought,” “design” and “intelligence” over other kinds of causes.  But (he says) there are many more “springs” (causes) in the universe than these. In the 19th century, known active causes at work in nature are “heat and cold, attraction and repulsion and a hundred others which fall under daily observation.” (19)  If I observe that water in my kettle is boiling, I will say that this is due to the high heat of the fire under the kettle.  If I set a magnet down next to my metal tweezers, and the tweezers slide toward the magnet, I say that the magnet causes the tweezers to slide toward it. What I don’t say is “Thought and intelligence are the cause of these effects.”

Of course, there are now more complex physical explanations of these phenomena, using different terminology. Scientists use the words “thermal energy” to explain the change of “the state” of water from still to boiling The phrase now used for magnetic attraction is particle exchange, “a general feature of quantum field theory.”

I confess to not knowing much about thermal energy and quantum field theory.  But my point is that if Philo (Hume) is right in saying that there are many different causes of events in nature, and the causal activity of thought and intelligence is only one of these, then without producing any empirical evidence at all, it is a fallacy to conclude that the origin of the universe, galaxies, stars, planets, human beings, trees, and other plants are all the product of an intelligent designer. We might as well say that the universe “sprouted” from seed or emerged (born) from the body of an animal. And if it is objected that the process of sprouting from seed or emerging from an animal body could only have been planned and designed by an intelligent being, then this begs the question, “Of all the many causes of events that we know to exist, why should we choose intelligent design to explain the origin of the universe?”  

Have worlds ever been formed under your eye, and have you had leisure to observe the whole progress of the phenomenon, from the first appearance of order to its final consummation? If you have, then cite your experience, and deliver your theory. (Dialogues, 22)

Finally, it is important to remember that analogical arguments are inductive, proving the probability of the conclusions, not certainty. As such, inductive arguments do not belong in the philosopher’s toolbox.  Inductive arguments produce conclusions from empirical data. Scientists gather empirical data, make observations, and do experiments.  Philosophers think about concepts and the conclusions they draw from their analyses are certain, not probable.

[Get your copy now.  Click on the book cover image above.]

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